I had some hot-engine issues a couple of months ago. I ended up getting a new three-row aluminum radiator, new water pump, new Summit six-blade fan, new hoses, new spring for the lower hose, new thermostat, and miscellaneous gaskets blah blah blah. Took her on my 20-mile test loop at ~70MPH, and she never went over half-way on the temp gauge. Yay! My troubles were over! Yesterday, I had to go out of town. Outside temps were just under 100F. She did fine on the hill going out of the valley. I tried passing a semi, taking it up to 100MPH before the road narrowed. Looked down at the gauge, and it was almost to the first hot line. Dropped back to 65MPH, but the gauge kept climbing. After about five miles, I was boiling over. So, what next? Do I just figure that this particular block runs hot, and the cooling system can't shed the heat? Do I retest my thermostat? I never see a drop in temps as the car warms up, so I have to assume the 'stat is opening and not telling me. Joseph
Do you have a fan shroud? I test thermostats by boiling them in a pan of water and seeing if/when they open. or just remove the thermostat and see if you get a different result (not a long term solution though)
I hate to be the bearer of any bad news, but I'm wondering if you have a failing head gasket? My '89 351W Bronco developed this sort of a problem, getting up to temp, then when the errant head and gasket opened up, the resulting cylinder pressure would push the coolant past the rad cap. I found out it was pressure when I shut off the engine, and the 'boil-over' would peter out.
Wouldn't I have oil in the coolant, then? I've never seen any sign of oil in the coolant, or coolant in the oil. How would I test for this? Jimbob suggested tiny bubbles in the coolant; would they remain in the coolant after it had cooled? Joseph
Right, but an overheating engine can also bubble. He would need to use a combustion gas detector to confirm whether it's only overheating, or overheating due to compression loss. And, oil doesn't necessarily get in the coolant.
So it sounds like I just have to bite the bullet, and replace the head gaskets not knowing whether they need replacing or not. Could be worse, I suppose. I don't know how, but it could be worse. Joseph
Dang it! I just realized that in order to take the heads off, I need to remove the intake manifold, too! This doesn't sound fun anymore. Joseph
You will only get oil in the coolant if the part of the gasket that separates them has gone. Sometimes the part between the water jacket and cylinder goes and this is how you get combustion in the coolant but no oil. The tiny bubbles will be evident after you have driven it as it's the combustion gasses escaping into the coolant and over pressurizing it. Also what shape is the block in? If the waterways are heavily corroded then that can cause overheating due to inefficient heat transfer.
Yeah, it took a few minutes to process what I needed to do. All right! Ordered and on its way! Joseph
I didn't have any bubbles when I checked it at lunch. My morning commute is ~7 miles. I thought about corrosion the first time, so I ran one of those off-the-shelf degunkers. Some people say they're great, some people say they're useless. I got dirty water out at the end, but no chunks of anything, or dirt. Joseph
Other than when it boiled over are you loosing coolant? It is very possible that you have a blown head gasket but there are usually tell tail signs that something is wet that shouldn't be. If your block is greasy/grimy there may be coolant in that and it would be worth a few cans of de-greaser and a power wash just to see what you actually have. If you don't find it there I would start thinking about freeze plugs and a good internal engine flush and scrape/brush as 72GTVA suggested. As noted above also a fan shroud that covers about 1/2 the blade and essentially seals the radiator can really make a difference. Food for thought. Cheers, Doc
They make a test kit that detects combustion gases in your cooling system...I have one...it works. You draw the expanding gasses from the radiator neck through a test liquid that changes color when certain compounds, which are consistent with combustion, are present. The fluid starts out blue and turns a bright green/yellow color, if memory serves. A fan shroud is only useful at rest or relatively low speeds. Your issue is at speed... more indicative of a crack, head gasket, or possibly severely retarded ignition timing (since you've eliminated the other causes that fit the scenario). I've only seen oil in coolant when something catastrophic has happened...usually, its coolant where oil should be. If you change your head gaskets, be sure to check the flatness of both heads and block with a precision straight edge. Don't just blindly replace the gaskets...make sure you have flat (unwarped) parts going back together.
Retarded engine timing can cause overheating? I didn't realize that. I don't remember what it is exactly, but I think it's around 12* BTDC. Easy enough to check this weekend ,though. I just ordered one of those kits to check for combustion gasses. I'll be checking for that on the weekend, too. Joseph
12* initial. What is your centrifugal advance at 2500 RPM? What is your total advance (centrifugal + vacuum) at 2500? How new is the timing chain and gears? Is it stock? Is it original?
I'm embarrassed to say that I don't know my centrifugal/total advance. It never, ever pings, under any conditions, on regular gas (87 octane), so it's not on the leading edge. When I got the Ranchero last year, I did some initial stuff, but then had to move on to higher priorities (Today, I noticed that I'm not getting anything from the front drum brakes, because I keep breaking traction in the rear. Since stopping is a high priority, my overheating woes might be put on the back shelf). I also don't know what kind of vacuum it's pulling, because there aren't any "extra" ports to tie into (C4 has a hard line all the way to the manifold, manual brakes, no manifold vacuum port on carb; I can probably use the PCV port, but have to rig up or find an adaptor). As for the timing chain, no idea. The engine isn't stock, or original. It left Ford with a 260, but the previous owner swapped in a 289 (unless he lied). I know it has 302 heads, but I don't know any particulars about them (I guess I'll find out if I need to replace the head gaskets). It still has a generator (probably from the original 260, probably because he didn't want to change the wiring), and it has a water pump from a 260 or older 289 (the design is slightly different than later water pumps). Sounds like I have some data-scrounging to do this weekend. Joseph
I made the mistake of forgetting to tighten the distributor hold-down bolt once. It allowed the distributor to go WAY retarded, and it overheated so badly I had to pull over & let it cool several times to get back home. Another thought may be that the block has been re-bored too far, like .060 oversize. I always hear stories of overheating in those situations.
As odd as it sounds, I can probably check that. I have one of those endoscope doo-dads for my cell phone. I can probably pull a plug, feed in the doo-dad, and see if there's any kind of stamp on the top of the piston. Joseph
